Add macro to compile time check if a path is valid (#3288)

Author: tcanabrava

Cargo.lock

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning].
 # Unreleased
 
 - **fixed:** Fix a broken link in the documentation of `ErasedJson` ([#3186])
+- **added:** Add `vpath!` for compile time path verification on static paths. ([#3288])
 
 [#3186]: https://github.com/tokio-rs/axum/pull/3186
 

axum-extra/CHANGELOG.md

@@ -58,6 +58,7 @@ http-body = "1.0.0"
 http-body-util = "0.1.0"
 mime = "0.3"
 pin-project-lite = "0.2"
+rustversion = "1.0.9"
 serde = "1.0"
 tower = { version = "0.5.2", default-features = false, features = ["util"] }
 tower-layer = "0.3"

axum-extra/Cargo.toml

@@ -25,6 +25,56 @@ pub use axum_macros::TypedPath;
 #[cfg(feature = "typed-routing")]
 pub use self::typed::{SecondElementIs, TypedPath};
 
+// Validates a path at compile time, used with the vpath macro.
+#[rustversion::since(1.80)]
+#[doc(hidden)]
+pub const fn __private_validate_static_path(path: &'static str) -> &'static str {
+    if path.is_empty() {
+        panic!("Paths must start with a `/`. Use \"/\" for root routes")
+    }
+    if path.as_bytes()[0] != b'/' {
+        panic!("Paths must start with /");
+    }
+    path
+}
+
+/// This macro aborts compilation if the path is invalid.
+///
+/// This example will fail to compile:
+///
+/// ```compile_fail
+/// use axum::routing::{Router, get};
+/// use axum_extra::vpath;
+///
+/// let router = axum::Router::<()>::new()
+///     .route(vpath!("invalid_path"), get(root))
+///     .to_owned();
+///
+/// async fn root() {}
+/// ```
+///
+/// This one will compile without problems:
+///
+/// ```no_run
+/// use axum::routing::{Router, get};
+/// use axum_extra::vpath;
+///
+/// let router = axum::Router::<()>::new()
+///     .route(vpath!("/valid_path"), get(root))
+///     .to_owned();
+///
+/// async fn root() {}
+/// ```
+///
+/// This macro is available only on rust versions 1.80 and above.
+#[rustversion::since(1.80)]
+#[macro_export]
+macro_rules! vpath {
+    ($e:expr) => {
+        const { $crate::routing::__private_validate_static_path($e) }
+    };
+}
+
 /// Extension trait that adds additional methods to [`Router`].
 pub trait RouterExt<S>: sealed::Sealed {
     /// Add a typed `GET` route to the router.